Geochemical heterogeneity and element mobility in deeply subducted oceanic crust; insights from high-pressure mafic rocks from New Caledonia

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• 作者：Spandler ; Carl ; Hermann ; Jö ; rg ; Arculus ; Richard ; Mavrogenes ; John
• 关键词：Subduction ; New Caledonia ; Oceanic crust ; Trace elements ; Metamorphism ; Eclogite
• 刊名：Chemical Geology
• 出版年：2004
• 出版时间：May 28, 2004
• 年：2004
• 卷：206
• 期：1-2
• 页码：21-42
• 全文大小：709 K

文摘

Bulk-rock major and trace element geochemistry of a range of eclogite, garnet blueschist and garnet amphibolite rocks from northern New Caledonia has been determined in order to geochemically characterise subducted oceanic crust. The rocks experienced peak metamorphic conditions of 1.9 GPa and 600 °C and represent excellent samples of oceanic crust that was subducted to depths of approximately 60 km. The rocks can be divided into seven rock types that respectively have geochemical characteristics of enriched and normal mid-ocean ridge basalt, back-arc basin basalt, alkaline basalt, plagioclase-rich cumulate, seafloor-altered basalt and Fe–Ti basalt. All of the samples studied represent a single slice of oceanic crust interpreted to have formed in a back-arc or marginal basin setting. Examination of modern oceanic crust suggests that most subducting crust also contains a diverse range of mafic rock-types. The presence of minor amounts of alkaline and seafloor-altered basalts in the slab can greatly influence the recycling of incompatible elements and the depth of fluid release during subduction.